scftorture: Count single_rpc offline failures in statistics outputgrafted

scf_torture_stats_print() aggregates each invoker thread's counters
into a local scf_statistics structure before printing, but the
n_single_rpc_ofl field is missing from the aggregation loop.  As a
result, the "single_rpc_ofl" value printed in the statistics line is
always zero, even when smp_call_function_single() invocations for the
RPC test have failed due to offline CPUs and been counted by the
invoker threads.

Add the missing accumulation so that the printed value reflects the
actual counts.

Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

1 files changed, 224 insertions, 0 deletions

diff --git a/rust/pin-init/examples/mutex.rs b/rust/pin-init/examples/mutex.rs
new file mode 100644
index 000000000..35ecb5f68
--- /dev/null
+++ b/rust/pin-init/examples/mutex.rs
@@ -0,0 +1,224 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+#![allow(clippy::undocumented_unsafe_blocks)]
+#![cfg_attr(feature = "alloc", feature(allocator_api))]
+#![allow(clippy::missing_safety_doc)]
+
+use core::{
+    cell::{Cell, UnsafeCell},
+    marker::PhantomPinned,
+    ops::{Deref, DerefMut},
+    pin::Pin,
+    sync::atomic::{AtomicBool, Ordering},
+};
+#[cfg(feature = "std")]
+use std::{
+    sync::Arc,
+    thread::{self, sleep, Builder, Thread},
+    time::Duration,
+};
+
+use pin_init::*;
+#[allow(unused_attributes)]
+#[path = "./linked_list.rs"]
+pub mod linked_list;
+use linked_list::*;
+
+pub struct SpinLock {
+    inner: AtomicBool,
+}
+
+impl SpinLock {
+    #[inline]
+    pub fn acquire(&self) -> SpinLockGuard<'_> {
+        while self
+            .inner
+            .compare_exchange(false, true, Ordering::Acquire, Ordering::Relaxed)
+            .is_err()
+        {
+            #[cfg(feature = "std")]
+            while self.inner.load(Ordering::Relaxed) {
+                thread::yield_now();
+            }
+        }
+        SpinLockGuard(self)
+    }
+
+    #[inline]
+    #[allow(clippy::new_without_default)]
+    pub const fn new() -> Self {
+        Self {
+            inner: AtomicBool::new(false),
+        }
+    }
+}
+
+pub struct SpinLockGuard<'a>(&'a SpinLock);
+
+impl Drop for SpinLockGuard<'_> {
+    #[inline]
+    fn drop(&mut self) {
+        self.0.inner.store(false, Ordering::Release);
+    }
+}
+
+#[pin_data]
+pub struct CMutex<T> {
+    #[pin]
+    wait_list: ListHead,
+    spin_lock: SpinLock,
+    locked: Cell<bool>,
+    #[pin]
+    data: UnsafeCell<T>,
+}
+
+impl<T> CMutex<T> {
+    #[inline]
+    pub fn new(val: impl PinInit<T>) -> impl PinInit<Self> {
+        pin_init!(CMutex {
+            wait_list <- ListHead::new(),
+            spin_lock: SpinLock::new(),
+            locked: Cell::new(false),
+            data <- unsafe {
+                pin_init_from_closure(|slot: *mut UnsafeCell<T>| {
+                    val.__pinned_init(slot.cast::<T>())
+                })
+            },
+        })
+    }
+
+    #[inline]
+    pub fn lock(&self) -> Pin<CMutexGuard<'_, T>> {
+        let mut sguard = self.spin_lock.acquire();
+        if self.locked.get() {
+            stack_pin_init!(let wait_entry = WaitEntry::insert_new(&self.wait_list));
+            // println!("wait list length: {}", self.wait_list.size());
+            while self.locked.get() {
+                drop(sguard);
+                #[cfg(feature = "std")]
+                thread::park();
+                sguard = self.spin_lock.acquire();
+            }
+            // This does have an effect, as the ListHead inside wait_entry implements Drop!
+            #[expect(clippy::drop_non_drop)]
+            drop(wait_entry);
+        }
+        self.locked.set(true);
+        unsafe {
+            Pin::new_unchecked(CMutexGuard {
+                mtx: self,
+                _pin: PhantomPinned,
+            })
+        }
+    }
+
+    #[allow(dead_code)]
+    pub fn get_data_mut(self: Pin<&mut Self>) -> &mut T {
+        // SAFETY: we have an exclusive reference and thus nobody has access to data.
+        unsafe { &mut *self.data.get() }
+    }
+}
+
+unsafe impl<T: Send> Send for CMutex<T> {}
+unsafe impl<T: Send> Sync for CMutex<T> {}
+
+pub struct CMutexGuard<'a, T> {
+    mtx: &'a CMutex<T>,
+    _pin: PhantomPinned,
+}
+
+impl<T> Drop for CMutexGuard<'_, T> {
+    #[inline]
+    fn drop(&mut self) {
+        let sguard = self.mtx.spin_lock.acquire();
+        self.mtx.locked.set(false);
+        if let Some(list_field) = self.mtx.wait_list.next() {
+            let _wait_entry = list_field.as_ptr().cast::<WaitEntry>();
+            #[cfg(feature = "std")]
+            unsafe {
+                (*_wait_entry).thread.unpark()
+            };
+        }
+        drop(sguard);
+    }
+}
+
+impl<T> Deref for CMutexGuard<'_, T> {
+    type Target = T;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        unsafe { &*self.mtx.data.get() }
+    }
+}
+
+impl<T> DerefMut for CMutexGuard<'_, T> {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        unsafe { &mut *self.mtx.data.get() }
+    }
+}
+
+#[pin_data]
+#[repr(C)]
+struct WaitEntry {
+    #[pin]
+    wait_list: ListHead,
+    #[cfg(feature = "std")]
+    thread: Thread,
+}
+
+impl WaitEntry {
+    #[inline]
+    fn insert_new(list: &ListHead) -> impl PinInit<Self> + '_ {
+        #[cfg(feature = "std")]
+        {
+            pin_init!(Self {
+                thread: thread::current(),
+                wait_list <- ListHead::insert_prev(list),
+            })
+        }
+        #[cfg(not(feature = "std"))]
+        {
+            pin_init!(Self {
+                wait_list <- ListHead::insert_prev(list),
+            })
+        }
+    }
+}
+
+#[cfg_attr(test, test)]
+#[allow(dead_code)]
+fn main() {
+    #[cfg(feature = "std")]
+    {
+        let mtx: Pin<Arc<CMutex<usize>>> = Arc::pin_init(CMutex::new(0)).unwrap();
+        let mut handles = vec![];
+        let thread_count = 20;
+        let workload = if cfg!(miri) { 100 } else { 1_000 };
+        for i in 0..thread_count {
+            let mtx = mtx.clone();
+            handles.push(
+                Builder::new()
+                    .name(format!("worker #{i}"))
+                    .spawn(move || {
+                        for _ in 0..workload {
+                            *mtx.lock() += 1;
+                        }
+                        println!("{i} halfway");
+                        sleep(Duration::from_millis((i as u64) * 10));
+                        for _ in 0..workload {
+                            *mtx.lock() += 1;
+                        }
+                        println!("{i} finished");
+                    })
+                    .expect("should not fail"),
+            );
+        }
+        for h in handles {
+            h.join().expect("thread panicked");
+        }
+        println!("{:?}", *mtx.lock());
+        assert_eq!(*mtx.lock(), workload * thread_count * 2);
+    }
+}